CYTOGENETIC STUDIES FOLLOWING HIGH DOSAGE PATERNAL IRRADIATION IN THE MEALY BUG PLANOCOCCUS CITRI. I. CYTOLOGY OF X$sup 1$ EMBRYOS
In cultures of the mealy bug, following high dosage paternal Co/sup 60/ gamma irradiation (60000--120000 rep), the survivors are mostly female (an increase of 30 to 40% above the unirradiated control value) whereas very few males survive (about 5% of control value). After lower doses of paternal irradiation (PI), however, few or no females survive while the normal number of males survive. The females developing after high dosage PI are gynogenetic and are triploid or diploid, or 3N/2N or 2N/N mosaics. The cytology of X/sub 1/ embryos following 90000 rep is described and compared with that of embryos following lower doses (8000 r) of PI and unirradiated controls, to illustrate the chromosomal mechanisms leading to the production of gynogenetic females and the probable reasons for lethality of X/sub 1/ males after heavy PI. It was shown that triploid females stem from a fusion nucleus of the first and second polar bodies. This triploid polar nucleus, which normally participates in the formation of a polyploid sector in the yourg embryo, undertakes successful embryogeny in many embryos when the zygote nucleus is unable to do so because of the heavily damaged paternal complement of chromosomes. Since the chromosomes are characterized by holokinetic activity, the irradiated paternal set mandsges to divide with the matennal complement but does not always segregate as successfully. Restitution divisions of the zygotic nuclei result in haploid, hyperhaploid, diploid, and polyploid nuclei. Most of the diploid gynogenetic females probably originate from diploid nuclei of zygotic origin, although it is possible that a few diploid females and the 2N/N mosaic females develop from polar bodies. (BBB)
- Research Organization:
- Univ. of California, Berkeley
- Sponsoring Organization:
- USDOE
- NSA Number:
- NSA-18-005029
- OSTI ID:
- 4145466
- Journal Information:
- Chromosoma (West Germany), Vol. Vol: 14; Other Information: Orig. Receipt Date: 31-DEC-64
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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